No reason to upgrade the *kernel*

However, a PCMCIA driver upgrade might be useful. Since this is not
the newest version of Mandrake, presumably you're running an older
version of the PCMCIA drivers.
What do you mean when you say the ethernet device "crashes"?
You can upgrade your PCMCIA drivers (including the 3c575_cb driver)
without touching your kernel or even rebooting.
-- Dave